Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
Tejun Heo | 6d66f5c | 2007-09-20 17:31:38 +0900 | [diff] [blame] | 2 | * fs/sysfs/symlink.c - sysfs symlink implementation |
| 3 | * |
| 4 | * Copyright (c) 2001-3 Patrick Mochel |
| 5 | * Copyright (c) 2007 SUSE Linux Products GmbH |
| 6 | * Copyright (c) 2007 Tejun Heo <teheo@suse.de> |
| 7 | * |
| 8 | * This file is released under the GPLv2. |
| 9 | * |
| 10 | * Please see Documentation/filesystems/sysfs.txt for more information. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 11 | */ |
| 12 | |
| 13 | #include <linux/fs.h> |
Tejun Heo | 5a0e3ad | 2010-03-24 17:04:11 +0900 | [diff] [blame] | 14 | #include <linux/gfp.h> |
Greg Kroah-Hartman | ceeee1f | 2002-04-09 12:14:34 -0700 | [diff] [blame] | 15 | #include <linux/mount.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 16 | #include <linux/module.h> |
| 17 | #include <linux/kobject.h> |
| 18 | #include <linux/namei.h> |
Dave Young | 869512a | 2007-07-26 14:53:53 +0000 | [diff] [blame] | 19 | #include <linux/mutex.h> |
David P. Quigley | ddd29ec | 2009-09-09 14:25:37 -0400 | [diff] [blame] | 20 | #include <linux/security.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 21 | |
| 22 | #include "sysfs.h" |
| 23 | |
Cornelia Huck | 36ce6da | 2008-06-10 11:09:08 +0200 | [diff] [blame] | 24 | static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target, |
| 25 | const char *name, int warn) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 26 | { |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 27 | struct sysfs_dirent *parent_sd = NULL; |
| 28 | struct sysfs_dirent *target_sd = NULL; |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 29 | struct sysfs_dirent *sd = NULL; |
Tejun Heo | fb6896d | 2007-06-14 04:27:24 +0900 | [diff] [blame] | 30 | struct sysfs_addrm_cxt acxt; |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 31 | int error; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 32 | |
Greg Kroah-Hartman | ceeee1f | 2002-04-09 12:14:34 -0700 | [diff] [blame] | 33 | BUG_ON(!name); |
| 34 | |
Eric W. Biederman | 7d0c7d6 | 2007-08-20 21:36:30 +0900 | [diff] [blame] | 35 | if (!kobj) |
| 36 | parent_sd = &sysfs_root; |
| 37 | else |
Tejun Heo | 608e266 | 2007-06-14 04:27:22 +0900 | [diff] [blame] | 38 | parent_sd = kobj->sd; |
Greg Kroah-Hartman | ceeee1f | 2002-04-09 12:14:34 -0700 | [diff] [blame] | 39 | |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 40 | error = -EFAULT; |
Tejun Heo | 608e266 | 2007-06-14 04:27:22 +0900 | [diff] [blame] | 41 | if (!parent_sd) |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 42 | goto out_put; |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 43 | |
Tejun Heo | 608e266 | 2007-06-14 04:27:22 +0900 | [diff] [blame] | 44 | /* target->sd can go away beneath us but is protected with |
Tejun Heo | 5f99532 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 45 | * sysfs_assoc_lock. Fetch target_sd from it. |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 46 | */ |
Tejun Heo | 5f99532 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 47 | spin_lock(&sysfs_assoc_lock); |
Tejun Heo | 608e266 | 2007-06-14 04:27:22 +0900 | [diff] [blame] | 48 | if (target->sd) |
| 49 | target_sd = sysfs_get(target->sd); |
Tejun Heo | 5f99532 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 50 | spin_unlock(&sysfs_assoc_lock); |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 51 | |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 52 | error = -ENOENT; |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 53 | if (!target_sd) |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 54 | goto out_put; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 55 | |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 56 | error = -ENOMEM; |
| 57 | sd = sysfs_new_dirent(name, S_IFLNK|S_IRWXUGO, SYSFS_KOBJ_LINK); |
| 58 | if (!sd) |
| 59 | goto out_put; |
Tejun Heo | a1da4df | 2007-07-18 16:14:45 +0900 | [diff] [blame] | 60 | |
Tejun Heo | b1fc3d6 | 2007-09-20 16:05:11 +0900 | [diff] [blame] | 61 | sd->s_symlink.target_sd = target_sd; |
Tejun Heo | a1da4df | 2007-07-18 16:14:45 +0900 | [diff] [blame] | 62 | target_sd = NULL; /* reference is now owned by the symlink */ |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 63 | |
Tejun Heo | fb6896d | 2007-06-14 04:27:24 +0900 | [diff] [blame] | 64 | sysfs_addrm_start(&acxt, parent_sd); |
Cornelia Huck | 36ce6da | 2008-06-10 11:09:08 +0200 | [diff] [blame] | 65 | if (warn) |
| 66 | error = sysfs_add_one(&acxt, sd); |
| 67 | else |
| 68 | error = __sysfs_add_one(&acxt, sd); |
Tejun Heo | 23dc279 | 2007-08-02 21:38:03 +0900 | [diff] [blame] | 69 | sysfs_addrm_finish(&acxt); |
Tejun Heo | fb6896d | 2007-06-14 04:27:24 +0900 | [diff] [blame] | 70 | |
Tejun Heo | 23dc279 | 2007-08-02 21:38:03 +0900 | [diff] [blame] | 71 | if (error) |
Tejun Heo | 967e35d | 2007-07-18 16:38:11 +0900 | [diff] [blame] | 72 | goto out_put; |
Tejun Heo | fb6896d | 2007-06-14 04:27:24 +0900 | [diff] [blame] | 73 | |
Tejun Heo | 967e35d | 2007-07-18 16:38:11 +0900 | [diff] [blame] | 74 | return 0; |
| 75 | |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 76 | out_put: |
| 77 | sysfs_put(target_sd); |
| 78 | sysfs_put(sd); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 79 | return error; |
| 80 | } |
| 81 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 82 | /** |
Cornelia Huck | 36ce6da | 2008-06-10 11:09:08 +0200 | [diff] [blame] | 83 | * sysfs_create_link - create symlink between two objects. |
| 84 | * @kobj: object whose directory we're creating the link in. |
| 85 | * @target: object we're pointing to. |
| 86 | * @name: name of the symlink. |
| 87 | */ |
| 88 | int sysfs_create_link(struct kobject *kobj, struct kobject *target, |
| 89 | const char *name) |
| 90 | { |
| 91 | return sysfs_do_create_link(kobj, target, name, 1); |
| 92 | } |
| 93 | |
| 94 | /** |
| 95 | * sysfs_create_link_nowarn - create symlink between two objects. |
| 96 | * @kobj: object whose directory we're creating the link in. |
| 97 | * @target: object we're pointing to. |
| 98 | * @name: name of the symlink. |
| 99 | * |
| 100 | * This function does the same as sysf_create_link(), but it |
| 101 | * doesn't warn if the link already exists. |
| 102 | */ |
| 103 | int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target, |
| 104 | const char *name) |
| 105 | { |
| 106 | return sysfs_do_create_link(kobj, target, name, 0); |
| 107 | } |
| 108 | |
| 109 | /** |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 110 | * sysfs_remove_link - remove symlink in object's directory. |
| 111 | * @kobj: object we're acting for. |
| 112 | * @name: name of the symlink to remove. |
| 113 | */ |
| 114 | |
Dmitry Torokhov | e3a15db | 2005-04-26 02:31:08 -0500 | [diff] [blame] | 115 | void sysfs_remove_link(struct kobject * kobj, const char * name) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 116 | { |
Mark Fasheh | a839c5a | 2008-01-29 14:35:18 -0800 | [diff] [blame] | 117 | struct sysfs_dirent *parent_sd = NULL; |
| 118 | |
| 119 | if (!kobj) |
| 120 | parent_sd = &sysfs_root; |
| 121 | else |
| 122 | parent_sd = kobj->sd; |
| 123 | |
| 124 | sysfs_hash_and_remove(parent_sd, name); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 125 | } |
| 126 | |
Eric W. Biederman | 7cb3294 | 2010-02-12 19:22:25 -0800 | [diff] [blame] | 127 | /** |
| 128 | * sysfs_rename_link - rename symlink in object's directory. |
| 129 | * @kobj: object we're acting for. |
| 130 | * @targ: object we're pointing to. |
| 131 | * @old: previous name of the symlink. |
| 132 | * @new: new name of the symlink. |
| 133 | * |
| 134 | * A helper function for the common rename symlink idiom. |
| 135 | */ |
| 136 | int sysfs_rename_link(struct kobject *kobj, struct kobject *targ, |
| 137 | const char *old, const char *new) |
| 138 | { |
| 139 | struct sysfs_dirent *parent_sd, *sd = NULL; |
| 140 | int result; |
| 141 | |
| 142 | if (!kobj) |
| 143 | parent_sd = &sysfs_root; |
| 144 | else |
| 145 | parent_sd = kobj->sd; |
| 146 | |
| 147 | result = -ENOENT; |
| 148 | sd = sysfs_get_dirent(parent_sd, old); |
| 149 | if (!sd) |
| 150 | goto out; |
| 151 | |
| 152 | result = -EINVAL; |
| 153 | if (sysfs_type(sd) != SYSFS_KOBJ_LINK) |
| 154 | goto out; |
| 155 | if (sd->s_symlink.target_sd->s_dir.kobj != targ) |
| 156 | goto out; |
| 157 | |
| 158 | result = sysfs_rename(sd, parent_sd, new); |
| 159 | |
| 160 | out: |
| 161 | sysfs_put(sd); |
| 162 | return result; |
| 163 | } |
| 164 | |
Kay Sievers | 2f90a85 | 2007-11-01 20:20:52 +0100 | [diff] [blame] | 165 | static int sysfs_get_target_path(struct sysfs_dirent *parent_sd, |
| 166 | struct sysfs_dirent *target_sd, char *path) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 167 | { |
Kay Sievers | 2f90a85 | 2007-11-01 20:20:52 +0100 | [diff] [blame] | 168 | struct sysfs_dirent *base, *sd; |
| 169 | char *s = path; |
| 170 | int len = 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 171 | |
Kay Sievers | 2f90a85 | 2007-11-01 20:20:52 +0100 | [diff] [blame] | 172 | /* go up to the root, stop at the base */ |
| 173 | base = parent_sd; |
| 174 | while (base->s_parent) { |
| 175 | sd = target_sd->s_parent; |
| 176 | while (sd->s_parent && base != sd) |
| 177 | sd = sd->s_parent; |
| 178 | |
| 179 | if (base == sd) |
| 180 | break; |
| 181 | |
| 182 | strcpy(s, "../"); |
| 183 | s += 3; |
| 184 | base = base->s_parent; |
| 185 | } |
| 186 | |
| 187 | /* determine end of target string for reverse fillup */ |
| 188 | sd = target_sd; |
| 189 | while (sd->s_parent && sd != base) { |
| 190 | len += strlen(sd->s_name) + 1; |
| 191 | sd = sd->s_parent; |
| 192 | } |
| 193 | |
| 194 | /* check limits */ |
| 195 | if (len < 2) |
| 196 | return -EINVAL; |
| 197 | len--; |
| 198 | if ((s - path) + len > PATH_MAX) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 199 | return -ENAMETOOLONG; |
| 200 | |
Kay Sievers | 2f90a85 | 2007-11-01 20:20:52 +0100 | [diff] [blame] | 201 | /* reverse fillup of target string from target to base */ |
| 202 | sd = target_sd; |
| 203 | while (sd->s_parent && sd != base) { |
| 204 | int slen = strlen(sd->s_name); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 205 | |
Kay Sievers | 2f90a85 | 2007-11-01 20:20:52 +0100 | [diff] [blame] | 206 | len -= slen; |
| 207 | strncpy(s + len, sd->s_name, slen); |
| 208 | if (len) |
| 209 | s[--len] = '/'; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 210 | |
Kay Sievers | 2f90a85 | 2007-11-01 20:20:52 +0100 | [diff] [blame] | 211 | sd = sd->s_parent; |
| 212 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 213 | |
| 214 | return 0; |
| 215 | } |
| 216 | |
| 217 | static int sysfs_getlink(struct dentry *dentry, char * path) |
| 218 | { |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 219 | struct sysfs_dirent *sd = dentry->d_fsdata; |
| 220 | struct sysfs_dirent *parent_sd = sd->s_parent; |
Tejun Heo | b1fc3d6 | 2007-09-20 16:05:11 +0900 | [diff] [blame] | 221 | struct sysfs_dirent *target_sd = sd->s_symlink.target_sd; |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 222 | int error; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 223 | |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 224 | mutex_lock(&sysfs_mutex); |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 225 | error = sysfs_get_target_path(parent_sd, target_sd, path); |
Tejun Heo | 3007e99 | 2007-06-14 04:27:23 +0900 | [diff] [blame] | 226 | mutex_unlock(&sysfs_mutex); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 227 | |
Tejun Heo | 2b29ac2 | 2007-06-14 03:45:15 +0900 | [diff] [blame] | 228 | return error; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 229 | } |
| 230 | |
Linus Torvalds | cc314ee | 2005-08-19 18:02:56 -0700 | [diff] [blame] | 231 | static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 232 | { |
| 233 | int error = -ENOMEM; |
| 234 | unsigned long page = get_zeroed_page(GFP_KERNEL); |
Armin Kuster | 557411e | 2009-04-29 07:29:59 -1000 | [diff] [blame] | 235 | if (page) { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 236 | error = sysfs_getlink(dentry, (char *) page); |
Armin Kuster | 557411e | 2009-04-29 07:29:59 -1000 | [diff] [blame] | 237 | if (error < 0) |
| 238 | free_page((unsigned long)page); |
| 239 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 240 | nd_set_link(nd, error ? ERR_PTR(error) : (char *)page); |
Linus Torvalds | cc314ee | 2005-08-19 18:02:56 -0700 | [diff] [blame] | 241 | return NULL; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 242 | } |
| 243 | |
Linus Torvalds | cc314ee | 2005-08-19 18:02:56 -0700 | [diff] [blame] | 244 | static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 245 | { |
| 246 | char *page = nd_get_link(nd); |
| 247 | if (!IS_ERR(page)) |
| 248 | free_page((unsigned long)page); |
| 249 | } |
| 250 | |
Arjan van de Ven | c5ef1c4 | 2007-02-12 00:55:40 -0800 | [diff] [blame] | 251 | const struct inode_operations sysfs_symlink_inode_operations = { |
Eric W. Biederman | c099aac | 2009-11-20 16:08:52 -0800 | [diff] [blame] | 252 | .setxattr = sysfs_setxattr, |
| 253 | .readlink = generic_readlink, |
| 254 | .follow_link = sysfs_follow_link, |
| 255 | .put_link = sysfs_put_link, |
Eric W. Biederman | e61ab4a | 2009-11-20 16:08:53 -0800 | [diff] [blame] | 256 | .setattr = sysfs_setattr, |
| 257 | .getattr = sysfs_getattr, |
| 258 | .permission = sysfs_permission, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 259 | }; |
| 260 | |
| 261 | |
| 262 | EXPORT_SYMBOL_GPL(sysfs_create_link); |
| 263 | EXPORT_SYMBOL_GPL(sysfs_remove_link); |
Simon Arlott | e0f4375 | 2010-05-10 09:31:11 +0000 | [diff] [blame] | 264 | EXPORT_SYMBOL_GPL(sysfs_rename_link); |